High density, high data rate recording systems, such as video and data recorders, require head materials with a high saturation magnetization (4.pi.M.sub.S), high permeability (.mu.) in the MHz frequency range, good tribological properties such as high wear resistance and high corrosion resistance.
Monolithic ferrite has been a material for record heads used in both magnetic disk and tape drives when the coercivity of the recording medium is less than 700 Oersteds (Oe) and the highest frequency is about ten megahertz (MHz). However, due to the need for high saturation magnetization and high frequency response, ferrite is not a good choice for newer applications.
Historically, Permalloy (NiFe) has been the magnetic material of choice for a record head of the thin film type. However, NiFe has poor wear resistance, and has a relatively low resistivity, causing permeability to decrease rapidly at higher frequencies due to eddy current losses.
Relative to monolithic ferrite, a sputter-deposited Sendust (FeSiAl) Alloy film offers a higher saturation magnetization, about 10 kilogauss (kG). Furthermore, a Sendust alloy has a relatively high resistivity and better wear resistance than Permalloy.
More recently, however, FeGaSi has been disclosed as a crystalline magnetic alloy having, compared to Sendust, both a higher saturation magnetization (about 13 kG) and lower coercivity (about 0.1 Oe). (See Journal of Applied Physics, Vol. 61, No. 8, Pages 3514 through 3519.) However, similar to Sendust, FeGaSi alloy films suffer from the disadvantage that their permeability, although almost constant in a range from 1 to 10 MHz, decreases rapidly for higher frequencies due to eddy current losses.
Following these developments, an FeGaSi-based alloy film having Ru as an additive is known in the art. FeRuGaSi has higher saturation magnetization than FeSiAl, although somewhat lower than FeGaSi, and an excellent soft magnetic property (low coercivity) and good wear resistance. This (FeRuGaSi) alloy was shown to be suitable for recording in a high frequency range near 100 MHz. (See Journal of Applied Physics, Vol. 64, No. 2, Pages 772 through 779.)
A need has therefore been felt for a magnetic core material which has as good or better soft magnetic properties (i.e., permeability and coercivity) than are currently available, but which (material) has an even higher saturation magnetization.